Telescopic homokinetic joint

ABSTRACT

A telescopic homokinetic joint which is capable of filtering vibrations coming from the driving means and is also devoid, or substantially devoid, of periodical internal friction. This result is obtained in a homokinetic joint comprising a first element including three pairs of planes which are evenly angularly spaced apart about a first axis, the planes of each pair being parallel to each other and to said axis, a second element defining three spherical bearing surfaces which are evenly angularly spaced apart about a second axis, and intermediate elements. The intermediate elements comprise planar surfaces which are respectively parallel to the planes and spherical surfaces which cooperate with the spherical bearing surfaces. According to the invention, rolling elements are interposed between the planar surfaces of the intermediate elements and the planes of the first element.

This application is a division of application Ser. No. 379,474, filedMay 18, 1982, now U.S. Pat. No. 4,490,126.

DESCRIPTION

The present invention relates to telescopic or sliding homokineticjoints employed in particular in automobile vehicle transmissions andespecially in front wheel drive vehicles between a power take-off shaftof the drive unit and a driving wheel.

It is known that combustion engines are the centre of vibrations ofamplitudes which vary in a wide frequency range of the order of 30 to300 Hertz. A sliding homokinetic joint should not only transmit thetorque at variable angles and elongations but also be infinitelypervious axially both in respect of a zero angle and in respect of amaximum angle of operation, so as to prevent the axial components of thevibrations of the engine from travelling toward the driving wheel andthe structure of the vehicle. Further, when it operates at an angle, thejoint should not itself introduce a periodical axial excitation capableof initiating vibrations in the structure of the vehicle.

Now, owing to operating friction whose amplitude varies cyclically,known sliding homokinetic joints have the following drawbacks:

The moments perpendicular to the axis of rotation, produced by friction,vary periodically and create corresponding excitations which may resultin resonances in the structure of the vehicle or in the transmissionshaft itself.

These periodic variations related to friction result from the manner inwhich the rolling members move, these members rolling or sliding underhigh load in accordance with the considered phase angle, thus producingvery high fluctuations in the resulting moment. Such an operation inwhich the same rolling member (such as a ball) changes from apractically pure rolling to a total sliding, is completely differentfrom that of the ball bearing in which the sliding rate is low andpractically constant.

There has moreover been described in French Pat. No. 1 341 628 filed onSept. 18, 1962 in the name of GLAENZER SPICER a homokinetic jointcomprising a first element defining three pairs of planes which areevenly angularly spaced apart about a first axis, the plane of each pairbeing parallel therebetween and to said first axis, a second elementdefining three spherical bearing surfaces evenly angularly spaced apartabout a second axis, and intermediate elements comprising, on one hand,planar surfaces respectively parallel to said planes and, on the otherhand, spherical surfaces which cooperate with said spherical bearingsurfaces.

However, such a joint cannot be used in practice owing to the periodicaldisturbances produced thereby. Thus, under the transmission of torque,the frictional forces vary as a function of the angle of rotation; thisvariation may be represented by a stepped curve having three cycles perrevolution. The break moment due to these frictions consequently vary inaccordance with a sawtooth curve having six cycles per revolution. Themagnitude of these variations renders them quite unacceptable, inparticular in the application envisaged hereinbefore.

An object of the invention is consequently to provide a telescopichomokinetic joint which is capable of filtering the vibrations comingfrom the driving means and which is also devoid, or substantiallydevoid, of periodical internal friction met with in the prior art. Sucha joint must, on the contrary, have a friction moment which is constantin magnitude and in direction and permit a very free slidingirrespective of the angle at which it operates and must not produceperiodical axial stresses.

This is achieved in a homokinetic joint of the type comprising a firstelement including three pairs of planes which are evenly angularlyspaced apart about a first axis, the planes of each pair being parallelto one another and to said first axis, a second element defining threespherical bearing surfaces which are evenly angularly spaced apart abouta second axis, and intermediate elements comprising, on one hand, planarsurfaces respectively parallel to said planes and, on the other hand,spherical surfaces which cooperate with said spherical bearing surfaces,wherein rolling elements are interposed between the planar surfaces ofthe intermediate elements and the planes of the first element, saidrolling elements being disposed in three sub-assemblies each comprisingtwo rows of rolling elements retained by cages.

According to other features:

the rows of rolling elements extend on a length exceeding the length ofthe gap between the planar surfaces between which they are disposed;

each cage comprises two opposed sides each carrying a row of rollingelements, said two sides being interconnected at their ends by endconnection or bridge regions;

the cages have a generally rectangular shape;

the rolling elements are needles;

elastically yieldable means are provided between each cage and theelement comprising the pairs of planes for biasing each cage to a meanposition;

said elastically yieldable means comprise at least one spider memberhaving three branches with the ends of the branches engaged on thebridges of the cages, and at least one spring interposed between saidspider member and the element defining the rolling planes;

the pairs of rolling planes are defined by wings which extend radiallyoutwardly from a centre shaft and the concave spherical surfaces aredefined in an outer element, the intermediate elements having aplanar-convex shape;

the pairs of rolling planes are defined on an outer element in the shapeof a tulip and the convex spherical bearing surfaces are defined by acentre element in the shape of a tripod, the intermediate elementshaving a planar-concave shape;

the pairs of rolling planes are defined by wings which extend radiallyinwardly from an outer element and the concave spherical bearingsurfaces are defined by a centre element, the intermediate elementshaving a planar-convex shape.

The invention will be described in more detail hereinafter withreference to the accompanying drawings which are given solely by way ofexample and in which:

FIG. 1 is a longitudinal sectional view of a joint according to theinvention;

FIG. 2 is a sectional view taken on line 2--2 of FIG. 1;

FIG. 3 is a sectional view taken on line 3--3 of FIG. 2;

FIG. 4 is a sectional view taken on line 4--4 of FIG. 3;

FIG. 5 is a detail view of the mounting of the needles in a cage;

FIGS. 6 and 7 are partial sectional views of the manner of operation ofelastically yieldable return means for the cages;

FIG. 8 is a cross-sectional view of a modification;

FIG. 9 is a sectional view taken on line 9--9 of FIG. 8;

FIG. 10 is a cross-sectional view of another modification;

FIG. 11 is a sectional view taken on line 11--11 of FIG. 10;

FIG. 12 is a partial view of other elastically yieldable return means.

The joint shown in FIGS. 1 to 3 comprises a first element or"tri-planar" element 1 including a shaft section 2 which has an axisX--X and from which extend three radial wings 3 whose median planes areevenly spaced 120° apart about the axis X--X. This tri-planar elementdefines consequently three pairs of planes, the plane 4 of each pairbeing parallel to each other and to the axis X--X.

A second element having an axis Y--Y is constituted by a barrel 10 whichmay be connected, for example to driving means, by bolts fixed inapertures 11. This barrel comprises three openings 12 whose medianplanes are also disposed at 120° to each other above the axis Y--Y,which, in the position illustrated in the drawings, is in alignment withthe axis X--X. Concave spherical cavities 14 are defined in theconfronting sides of the openings 12.

Six intermediate elements 20 of planar-convex shape are interposedbetween the tri-planar element and the barrel. Their spherical surfaces21 are received in the spherical cavities 14 of the barrel and theirplanar surfaces 22 are disposed to be parallel to and at a distance fromthe planar surfaces 4 of the tri-planar element. Needles 23 are disposedbetween the confronting planar surfaces 4 and 22. Provided for each pairof planes are two parallel rows of needles which are maintained in acage 24 comprising two large side portions 25 which define cavities 26in which the needles are disposed, the large side portions 25 beinginterconnected at their ends by two bridges 27. These cages haveconsequently a generally rectangular shape. The cavities 26 are providedwith nose portions 28 for retaining the needles when they are locatedoutside the gap between the planar surfaces 4, 22 (FIG. 5). The cagesare radially maintained in position relative to the tri-planar elementbetween shoulders 5 and 6.

The wings 3 of the tri-planar element have an axial length which exceedsthe diameter of the planar-convex elements 20 and the cages 24 have alength exceeding the length of said wings.

Means are provided for returning the cages of the needles to a medianposition. These means comprise two spider members 30 having threebranches 31 and made from hardened pressed sheet metal. A bridge of eachof the cages is retained between two confronting branches of the twospider members. The latter are gripped between a head 32 of a rod 33 anda spring 34 mounted on the latter. The rod 33 is slidably mounted in arecess 7 formed in the element 1 and in a ring 8 fixed to the latter.This ring acts as a support for the spring 34 and for a second spring 35whose other end bears against an enlarged end portion 36 of the rod 33.

The operation and the advantages of such a joint are as follows. Whentransmitting a torque at an angle, the planar-convex elements 20oscillate and rotate as they are slidably supported in the concavespherical cavities 14 formed in the sides of the openings of the barrel.At the same time, the needles 23 roll along the confronting surfaces 4and 22 of the wings 3 and the elements 20.

Note that the clearance between these intermediate elements 20, theneedles 23 and the rolling planes 4 may be completely eliminated. Theremay even be provided a slight pre-stressing without adversely affectingthe smoothness of operation and without creating any hard point in theaxial sliding. This joint may consequently operate with no angular play,which constitutes an important quality.

The loading of the needles 23 and their unloading, depending on whetherthey enter the regions located between the intermediate elements 20 andthe wings 3 of the tri-planar element or whether they leave theseregions, occur progressively and smoothly, even under high torque, fortwo reasons:

First, the spherical domes 20 are more flexible on the edges whileremaining sufficiently strong. Second, the start of the loading occursonly on the median part of the needle.

Upon a sliding of the joint, the needles always roll in a directionparallel to the axis X--X of the shaft 2. During this time, theplanar-convex elements oscillate relative to their cavities defined inthe barrel. The sliding of these spherical surfaces during the rotationat an angle and under torque produces a resulting moment of constantvalue and fixed direction, which corresponds to the desired result.

When the joint operates at an angle, the alternating movement oftranslation of the planar-convex elements relative to the planes of thewings occurs in a pure rolling motion without resistance. Thisalternating movement therefore does not result in any fluctuation of thesliding moment and creates no periodical axial stress on the shaft.

Apart from the very free axial sliding at zero angle or at a large angleof operation, which completely filters the axial vibrations, thefeatures of the joint according to the invention also result in aperfect neutrality which is essential to the comfort of automobilevehicles.

The return device, shown in more detail in FIGS. 6 and 7, performs animportant function. Indeed, it permits:

1. The translation of all of the three cages toward the right or theleft, corresponding to the sliding of the joint respectively incompression on in extension.

2. The alternating differential translation of the three cages withdisplacements corresponding to one half of the displacement of theplanar convex elements relative to the corresponding planes of theelement 1, owing to the rotation of the joint at an angle.

In this case, the two spider members 30 assume an inclination whichroughly corresponds to one half of the relative inclination between theaxes X--X and Y--Y.

The springs 34, 35 bias the spider members 30 to a mean positionperpendicular to the axis of the rod 33. FIG. 7 represents an extremeposition in which the spring 34 is compressed while the spring 35 isextended. There results an axial force which tends to move the twospider members toward the right and therefore to recentre the cage, theforce designated by the arrow F¹ being larger than the force designatedby the arrow F². Further, these two forces create a return moment whichbiases the planes of the two spider members to a position perpendicularto the axis of the rod 33 and consequently to equalize the relativeaxial positions of the bridges and of the three cages.

FIGS. 8 and 9 show another arrangement of a slidable homokinetic jointaccording to the invention. This joint comprises a first element 101constituting a tripod element rigid with a shaft 102. This tripodelement carries three spherical balls 103 which are spaced 120° apartabout the axis of the tripod element. These spherical balls 103 aretruncated on flat surfaces 104 which are disposed perpendicular to theaxis of the tripod element so as to permit the mounting of theintermediate elements which will be described hereinafter.

A second element is formed by a tulip element 110 comprising threebranches or petal portions 111 which define therebetween runawaysconstituted by pairs of planes 112, the planes of each pair beingparallel to each other and parallel to the axis of the tulip element.

Disposed between the spherical balls 103 and the parallel planes 112 areintermediate elements 120 which are formed, in the illustratedembodiment, by U-structures comprising an end wall 121 and lateral walls122 which define, on one hand, a concave spherical inner surface 123cooperating with the ball 103 and, on the other hand, planar outersurfaces 124 which are parallel to the surfaces 112 constituting therunways. Rows of needles 125, retained as in the preceding embodiment bycages 126, are disposed between the confronting planar surfaces of thetulip element 110 and the intermediate elements 120.

These cages have a rectangular shape and include large side portions 127defining cavities 128 in which the needles are received, saidlongitudinal large sides being interconnected by transverse sideportions or bridges 129. The bridges are cut out internally in the shapeof an arc of a circle (at 129a) so as to allow the angular movement ofthe shaft 102.

The tulip element is surrounded by a cover 130 constituted by a metalformed-over sleeve defining a groove 131 in which a sealing bellows (notshown) can be fixed. This cover has three inwardly projecting portions132 located on the axis of the openings of the tulip element. Theseprojecting portions act as an abutment for the bridges 129 of each ofthe cages at the end of the extension travel of the joint.

Elastically yieldable return means for the cages are also provided asdiagrammatically shown on FIG. 9. The return means may be such as thosedescribed and illustrated in respect of the first embodiment.

A third modification is shown in FIGS. 10 and 11. The joint comprises afirst element or barrel 200 which is roughly cylindrical and from whichextend radially inwardly three wings 201 spaced 120° apart about theaxis of the element 200. These three wings each define two rollingplanes 202 limited by two radial shoulders 203. This barrel may comprisefixing aperatures 204 and a circular groove 205 for receiving the endportion of a sealing bellows (not shown).

The joint comprises a second element 210 which is rigid with a shaft 211and defines three concave spherical cavities 212 which are spaced 120°apart relative to the axis of the shaft 211.

Disposed between the two elements 200, 210 are intermediate elements 220constituted by planar-convex spherical domes, the spherical parts 221 ofwhich are received in the cavities 212 of the centre element 210 whereasthe planar surfaces 222 are parallel to the planes of the outer element200. Disposed, as in the foregoing embodiments, between the confrontingplanar surfaces are rows of needles 223 which are retained in cages 224.These cages have at their inner ends inclined surfaces 225 to permit therelative inclination of the shafts.

Further, return springs 226 are disposed between the end bridges 227,interconnecting two longitudinal side portions 228 of the cages, and theadjacent surfaces of the arms or wings 201 defining the rolling planes202. These bridges are also cut away at 227a.

In this arrangement, the runways are preferably formed by a broachingoperation in the same way as the guiding edges 203 for the cages.

The operation and the advantages are the same as those mentioned inrespect of the first embodiment.

FIG. 12 shows a particularly simple modification of the elasticallyyieldable means for returning the cages 300 relative to the element 301defining the rolling pins with which the needles 302 carried by thiscage cooperate. These means comprise a member 303 moulded from a plasticmaterial, eg. nylon, defining three branches 304 disposed at 120° toeach other. Each branch terminates in a clip or holder 305 or othersuitable means which engages on a bridge 306 of a cage. The centreportion of the member 303 defines a cavity 307 in which is fixed, forexample, screwed, a coil spring 308 whose other end portion is alsofixed in a cavity 309 in the element 301. Such return means may ofcourse be employed in the various embodiments of the joint describedhereinbefore.

Having now described my invention what we claim as new and desire tosecure by Letters Patent is:
 1. A homokinetic joint comprising:a firstelement having a first axis and including three portions which extendradially with respect to said first axis spaced 120° apart about saidfirst axis, each of said portions defining spherical bearing surfaces; asecond element having a second axis and defining three raceways whichare spaced 120° apart about said second axis, each said raceway beingconstituted by a pair of planar surfaces parallel to each other andparallel to said second axis, said surfaces defining therebetween a gap,each of said portions of the first element being located in the gapdefined between the planar surfaces of a respective raceway with saidspherical bearing surfaces facing said planar surfaces; intermediateelements disposed between said spherical bearing surfaces and saidplanar surfaces, said intermediate elements having planar surfacesdisposed parallel to and facing the planar surfaces of said raceways andhaving spherical bearing surfaces complementary and fitting with thespherical bearing surfaces of said first element; and rolling elementsdisposed between said planar surfaces of said raceways and said planarsurfaces of said intermediate elements, said rolling elements beingarranged in a linear manner to form three sub-assemblies, each saidsub-assembly including means for allowing both relative linear andangular displacements of said first and second elements, said allowingmeans including two linear rows of said rolling elements and cage meansretaining the rows of rolling elements, each said row of rollingelements having a length exceeding the length of the planar surfaces ofsaid intermediate elements.
 2. A joint according to claim 1, whereineach cage means comprises two opposed side portions and two bridgesinterconnecting the two side portions, each side portion retaining a rowof said rolling elements.
 3. A joint according to claim 2, wherein eachcage means has a generally rectangular shape.
 4. A joint according toclaim 1, wherein the intermediate elements are constituted byU-structures each comprising two sets of respectively planar and concavespherical surfaces.
 5. A joint according to claim 1, wherein the rollingelements are needles.
 6. A joint according to claim 1, wherein saidfirst element is a center element in the form of a tripod and saidsecond element is an exterior element in the shape of a tulip.
 7. Ajoint according to claim 1, wherein the cage means are so shaped in thevicinity of the ends thereof so as to permit angular movement of anadjacent shaft.
 8. A joint according to claim 1, comprising abutmentmeans for the cage means at the end of an extension travel of the firstand second elements of the joint.
 9. A joint according to claim 1,wherein the spherical bearing surfaces of said first element are convexand the intermediate elements have planar-concave shape.
 10. A jointaccording to claim 9, wherein the intermediate elements are constitutedby six planar-concave spherical domes.
 11. A joint according to claim 1,wherein return means are provided between each sub-assembly and one ofsaid first and second elements for elastically returning eachsub-assembly to a mean position relative to said one of said first andsecond elements.
 12. A joint according to claim 11, wherein each cagemeans comprises two opposed side portions and two bridgesinterconnecting the two side portions, each side portion retaining a rowof said rolling elements, and said return means comprises at least aspider member having three branches, end portions of the branches beingengaged on the bridges of the respective cage means, and at least aspring interposed between said spider member and the first element. 13.A joint according to claim 11, wherein said return means comprise atleast a return spring between each cage and an end surface of said firstelement.